strace is a debugging utility for tracing system calls and signals under Linux.

learn more… | top users | synonyms

2
votes
1answer
16 views

Sending a string to strace for “printf debugging”

While there are command line versions of strace for windows, the defacto GUI equivalent of strace on windows is Sysinternals procmon. In addition to letting you view file, registry, network and other ...
2
votes
1answer
23 views

Decode / summarise strace logs

OK, so it's no secret that strace produces vast amounts of output. (I'm aware there are various options to filter the output a bit.) Are there any tools to process a raw strace log into something ...
1
vote
1answer
30 views

Tracing the node process executing my script from “npm start”

I am attempting to debug a cli node project. Its easier to do npm start than npm install -g . && libgrabber. However, I'd like to run strace on the process. The output of strace -f on the npm ...
1
vote
1answer
85 views

Strace Hello World program

So I am trying to understand systemcalls with the following "Hello World!" program: #include <stdio.h> int main(){ printf("Hello World!\n"); return 0; } and then I run strace on the ...
6
votes
6answers
505 views

why strace ignores my alias for rm?

I have an alias set for my rm command. If I run alias command, this is what I get as output. alias rm='rm -i' Now, when I run the rm command it works fine as expected. rm ramesh rm: remove ...
0
votes
2answers
74 views

How does rsync encode filenames?

By using strace on the active rsync process, I can see output like: read(4, "9\0\0\7\1\10\0\1\10\0\1\10\0\1\10\0\1\10\0\1\10\0\1\10\0\1\10\0\1\10\0\1"..., 16384) = 61 write(3, ...
2
votes
1answer
61 views

strace works for some builtin commands

I'm trying to understand some kernel level concepts in Linux. I was checking on the difference between shell builtin commands and the other executable commands. This wonderful answer clearly tells ...
4
votes
0answers
124 views

Tracing executable without read permissions

I found some surprising behavior on Ubuntu 14.04 when using strace on an executable, which I do not have read permission on. I wonder if this is a bug, or if some standard mandates this obscure ...
2
votes
3answers
209 views

Can strace/ptrace cause a program to crash?

So recently, I was discussing strace with somebody, and they were asking what would happen if you straced a running process just as it was creating a network socket or something similar. Could this ...
5
votes
2answers
295 views

How to determine what instructions a process is executing?

I know about strace and ltrace, but that only tells me what system calls and library calls a process is executing, respectively. I would like to know exactly what instructions a process is executing. ...
1
vote
1answer
94 views

How to use pv with dd?

I'm trying to use dd with pv to write an iso to a usb drive. I did: iso="myiso.iso"; dd if="$iso" bs=1M | pv --eta --size $(ls -l "$iso" | awk '{print $5}') --progress --bytes --rate --wait > ...
2
votes
2answers
161 views

running strace for specific period of time

How to run strace on a user process for specific period of time, say 1 minute, without terminating the user process and without using Ctrl+C? I want to create a script to automating strace execution ...
1
vote
1answer
52 views

Apache suexec won't work with strace

I have an Apache instance with mod_suexec enabled. I'm trying to debug a problem and am starting Apache with strace to try and see what's happening. However, when I start Apache like this: # strace ...
2
votes
1answer
106 views

Make sense of this strace output

Can anyone make sense of this strace output? [pid 25302] read(34, "}B\311\204\n\250\347$\220\266kRb\304a^^\2504\303k\235\227T\223\16\231\306\277\254\256\306", 32) = 32 It's from a Linux system ...
0
votes
0answers
176 views

How do I make strace “decode” AF_NETLINK comminucation like with ioctl?

strace usually "deciphers" ioctls, showing what do they mean, even resolving network interface names and so on. But the same operation performed using AF_NETLINK stays opaque in strace. How to teach ...
1
vote
0answers
71 views

How to debug a semop failure?

Using a 2.6.30-gentoo-r4 Linux a very complex system of php code is executed (with 4.4.9-pl0-gentoo and 5.2.10-pl0-gentoo), which occasionally runs into a semaphore blocking problem. The call to the ...
2
votes
0answers
673 views

How is it that I can attach strace to a process that isn't in the output of ps?

I'm trying to debug why our integration tests are taking so long and it looks like they're hanging part way through. I logged onto our test service and saw the following behaviour: root@colossus:~# ...
0
votes
1answer
50 views

MC and MCedit take long time to start

I recently discovered that my MidnightCommander takes around 40 seconds for every startup and the same goes for McEdit. I access my machine only via ssh and of course I'm not logging in as root, only ...
1
vote
1answer
404 views

Too Much System Time

I have observed that when running CESM (a weather modeling application), the top command shows a great deal of time is spent on system calls, about 25% to 60%, and only 40% to 75% is used in user ...
2
votes
1answer
20 views

Retrieve system commands without reading sources

Sometimes I wonder how Linux programs achieve certain results knowing that they internally use system calls (system() or exec() in C programs). Given a working binary I wonder if it is possible to ...
1
vote
1answer
450 views

strace got message — SIGIO (I/O possible) @ 0 (0) ---

I'm trying to monitor serial port communication using strace -s9999 -o serialtrace.log -eread,write,ioctl command. After few normal logging messages I got guge amount of message --- SIGIO (I/O ...
0
votes
1answer
339 views

Monitor com port with strace

I have done small application in Java that writes to com port two strings -'dddd' and 'ffff'. I decided to look how it writes with thelp of strace -s9999 -o serialtrace.log -eread,write,ioctl And I ...
3
votes
1answer
72 views

How (if possible) can I terminate a specific blocker hanging a program?

I have a number of files open in my editor (geany). I managed to hang it doing a sort on a large list that I should have saved and just sent through a pipe to sort via command-line (I mapped one of ...
4
votes
1answer
89 views

Is strace a suitable tool for finding out where a program wrote to the filesystem?

I'd like to determine where a certain app (as an example, surf) writes to the filesystem in order to make sure it leaves no traces. Without a dedicated sandboxing system this probably isn't easy, but ...
6
votes
2answers
684 views

Is it possible to strace the builtin commands to Bash?

Inspired by this question, titled: When are the built-in commands loaded to memory, while attempting to answer this I tried the following command and was a bit surprised that I couldn't run it: $ ...
3
votes
2answers
3k views

How to 'strace' a unix domain socket?

Kind of hard to explain but I noticed when straceing the PID that has the socket open I cannot see any of the communication. How can I sit in the middle of a socket file to watch communication?
0
votes
2answers
349 views

How does strace know to use /bin/echo instead of failing on a built-in

When I do strace echo hello, I see it is using /bin/echo, but built-in echo should be found first. Is it a functionality of strace to skip built-in commands? strace -- version 4.5.19 I understand ...
3
votes
1answer
861 views

Why is brk(0) called?

On a first shell I run the command tail with no argument. On a second shell I kill the first tail using strace to monitor the system calls. qdii@nomada ~ $ strace kill 1713 execve("/bin/kill", ...
3
votes
2answers
2k views

Measure disk IO latencies of a running process

I'm trying to measure the disk IO latencies of a running process to make a histogram. I could do this with DTrace in operating systems that provide it (e.g. as in this Joyent paper), but my ...
3
votes
3answers
1k views

Command to trace rsh server to check behaviour of particular system call

I am working with rsh. I want to check the whole process from beginning to end. For that I used strace. Os name is CentOS. I am working on single machine, server and client are on same machine. My ...
2
votes
1answer
1k views

Why can't I use strace with rsh?

If I run rsh, it works, but prints some strange “Connection refused” messages at the beginning: $ rsh localhost pwd connect to address 127.0.0.1 port 544: Connection refused Trying krb4 rsh... ...
0
votes
2answers
175 views

How to detect particular system call called or not in a whole workflow?

EDIT No. 1 My task is mirroring , i.e., copying updated data from master server to all mirrors, by using rsync and rsh. But during rsync and rsh, I found some delay. My thinking is , the reason for ...
1
vote
0answers
94 views

Android strace error: “strace: 2: Syntax error: ”&“ unexpected”

I was using built-in strace given in /system/xbin/ directory in the emulator and it was giving me wrong set of system calls such as msgget() and msgrecv() which are not supported by Android even. I ...
4
votes
3answers
1k views

Stracing su and ssh shows the password. Is this a security flaw or am I missing something?

I'm currently fascinated by strace so, being new to it, I decided to play around a little. As suggested by the question title, I tried both strace su and strace ssh. Both commands displayed the ...
6
votes
1answer
3k views

piping strace to grep

I'm trying to run strace trough ccze, and the pipe doesn't work as expected. The command-line I'm running to test is sudo strace -p $(pgrep apache2) | grep open, and all lines are output, ignoring ...
3
votes
1answer
419 views

Plotting the sleep/wait chain of a process

I often want to know why a process in the middle of a pipeline is sleeping and not busy processing data. My current method is: find the pid of interest sudo strace -pt pid to get the blocking ...
7
votes
1answer
160 views

Finding where a process reads in a file

Is there a way to attach to a process and find out, not only which files it is reading from, but what the read locations (byte offsets) of those reads are? I tried using strace for this, but it ...
4
votes
2answers
387 views

ls behaves differently under strace

I don't know how to debug this situation: 1) I try to execute: ls /home/user 2) ls blocks and does not print anything. I assume it is because /home/user contains /home/user/sshfs_files, which is ...
8
votes
4answers
558 views

How could running strace be fixing my OpenGL issue?

Since a recent major upgrade to my distribution (PLD Linux), I have been having trouble with a whole slew of programs. As best I can tell, anything that touches OpenGL or PulseAudio segfaults. I'm ...
6
votes
1answer
288 views

Unkillable apache2 processes

After upgrading from debian lenny to squeeze (apache2 2.2.16-6+squeeze4 and php 5.3.10-1~dotdeb.1), my apache processes started to exit with segmentation fault. It happens every 5-30 minutes (for 1 ...
15
votes
3answers
7k views

List the files accessed by a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can list the files being accessed by a program and its children. ...
3
votes
1answer
608 views

Which processes should I NOT strace?

I've created a little function for strace'ing a set of the current user's processes by name: function pstrace() { local pattern="$1"; shift; prefixDashP $(pgrep -U $(whoami) $pattern) | ...
3
votes
1answer
142 views

Sample a few lines from an strace printout

I've got a process that I want to inspect with strace, but since it's printing out a lot of stuff, I would like to sample only a few lines every X seconds from it. Is there any way of doing that with ...